Bearings used for the steering columns of motorcycles are subject to bi-directional load, i.e., in both the radial direction and the axial (shaft) direction. Accordingly, angular contact ball or roller bearings are generally used. This gives rise to several problems.
The magnitude of the frictional resistance of the steering column, i.e., its turning friction torque, must be held within predetermined limits. It is possible to adjust this torque by tightening the nut on the steering column at the time the latter is attached to the head pipe. Angular contact ball bearings provide a wider adjustment range for the shaft tightening force than conical roller bearings, and hence facilitate higher loads.
However, the ball or roller bearings used in prior art steering mechanisms allowed only a rather small angle of swing.